Hajime Kazami, Shun-ichi Matsushita, Yoshihiro Emori, Takashi Murase, Masamichi Tsuyuki, Kunihiro Yamamoto, Hiroshi Matsuura, Shu Namiki and Takaaki Shiba
Fiber Raman amplifier (hereafter called Raman amplifier) is becoming popular for its superiority in characteristics. Because the Raman amplifier has a large polarization dependence of Raman gain, a number of designs are being proposed to reduce the influence, and a device known as depolarizer plays an important role among those designs. A depolarizer based on a 45° pliced polarization-maintaining fiber (PMF) is already in practical application. However, this depolarizer has problems such as, besides the necessity for large accommodation space, unsteady Raman gain due to the deterioration of degree of polarization (DOP), which is caused by temperature fluctuations in the amplifier. Accordingly, the authors have developed a crystal-type depolarizer recently, and succeeded in realizing miniaturization of the device as well as reduction of the temperature dependence of DOP. It is expected that this development help to promote popularization of Raman amplifiers as well as demand increase hereafter.